1. Field of the Invention
The present invention relates to a linear image sensor, and particularly to a linear image sensor with a shutter function.
2. Description of the Related Art
In a color linear image sensor in which a linear image sensor is used, conventionally, a plurality of linear image sensors are disposed. A plurality of image sensors correspond to different colors respectively. Generally, different color filters (for example, GREEN, BLUE, and RED) correspond to the respective linear image sensors in the arrays. A plurality of light-receiving elements, such as photodiodes, are disposed in lines on a semiconductor substrate in the linear image sensor in each array. The plurality of light-receiving elements correspond to each pixel. In such linear image sensor, signal charges that are photoelectrically converted by the light-receiving elements are sequentially transferred, whereby image signals corresponding to the respective pixels are sequentially outputted.
In a color linear image sensor that has a shutter function, the exposure is set for color filters with different colors respectively. In general, the exposure setting is performed by providing the linear image sensor in each array with a shutter gate and a shutter drain. Appropriate image data for each color can be obtained by this exposure setting.
The conventional structure of a linear image sensor is such that one side of an array of light-receiving elements of the image sensor is provided with a shutter gate and a shutter drain, and that the other side of same is provided with a charge reading section and a charge transfer section. Since the speed of the linear image sensor increases, there was a problem that the read time becomes long when reading out signals from the one side only. In order to respond to higher speed of the sensors, there has been proposed in the conventional linear image sensor a system in which two charge transfer sections are provided so as to hold therebetween the arrays of light-receiving elements and use the two charge transfer sections to read out signal charges. However, a shutter structure could not be provided to this system, thus it was difficult to achieve high quality picture.
For such technology, there is described a technology in Japanese Unexamined Patent Application Publication No. 2000-32216. In the technology described in Japanese Unexamined Patent Application Publication No. 2000-32216, one side of an array of light-receiving elements is provided with first and second charge transfer sections in parallel. By using this structure, the first charge transfer section near the array of light-receiving elements receives signal charges generated in the odd-numbered pixels, and the second charge transfer section which is far from the array of light-receiving elements receives signal charges generated in the even-numbered pixels, so as to respond to higher speed. On the other hand, in order to prevent increase of a line-to-line distance that is caused by providing a shutter structure section to each linear sensor, first to third linear image sensors having different sensitivities for incident light are disposed from the outer side in the order of highest sensitivity with respect to the incident light, and further a shutter gate and a shutter drain, which adjust the exposure for the only linear image sensor having the highest sensitivity for the incident light on the side where light comes, are provided. Such technology is also disclosed in Japanese Unexamined Patent Application Publication No. 9-205520.
Japanese Unexamined Patent Application Publication No. 60-120557 describes a solid-state image sensing device which has a structure to suppress a blooming.
When achieving high speed of the linear image sensor as described above, it was difficult to pursue a higher-quality picture.